Napped artificial leather and production method thereof

ABSTRACT

Disclosed is a production method of a napped artificial leather including the steps of: providing a fiber sheet including a non-woven fabric of ultrafine fibers with a fineness of 1 dtex or less that has been impregnated with a first elastic polymer; napping one or both surfaces of the fiber sheet to form a napped surface thereon; applying, to the napped surface, a resin solution containing a second elastic polymer having solubility in a predetermined solvent; and applying the predetermined solvent to the surface to which the resin solution is applied. Also disclosed is a napped artificial leather including a fiber sheet obtained by impregnating a first elastic polymer into a non-woven fabric that is an entangled body of ultrafine fibers with a fineness of 1 dtex or less, wherein the fiber sheet includes, on one or both surfaces thereof, a napped surface obtained by the ultrafine fibers, and a second elastic polymer is fixed to basal portions of the napped ultrafine fibers.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. Ser. No. 15/025,788,filed Mar. 29, 2016, pending.

TECHNICAL FIELD

The present invention relates to a napped artificial leather for use asa surface material for clothing, shoes, articles of furniture, carsheets, general merchandise, and the like. More particularly, theinvention relates to a napped artificial leather that has excellentpilling resistance, i.e., that is less likely to cause pilling, which isa phenomenon in which fibers on the surface are fuzzed due to frictionor the like and the fuzzed fibers are entangled to form small sphericalmasses.

BACKGROUND ART

Napped artificial leathers such as a suede-like artificial leather and anubuck-like artificial leather are conventionally known.

For example, PTL 1 below discloses a method of producing a nubuck-likeartificial leather that provides dense fluff and fine creases.Specifically, PTL 1 discloses a method of producing a nubuck-likeartificial leather in which, when an artificial leather substratecontaining an elastic polymer inside an ultrafine fiber-entanglednon-woven fabric is finished into a napped artificial leather, thefollowing steps are performed in order: applying a solvent capable ofswelling or dissolving the elastic polymer to one surface of theartificial leather substrate; napping at least the one surface to form anapped surface; applying the elastic polymer to the napped surface; andfurther napping the surface to which the elastic polymer has beenapplied.

CITATION LIST Patent Literature

[PTL 1] Japanese Laid-Open Patent Publication No. 2007-262616

SUMMARY OF INVENTION Technical Problem

The conventional napped artificial leathers tend to cause pilling.Pilling is problematic in that it degrades the appearance. It is anobject of the present invention to provide a napped artificial leatherhaving excellent pilling resistance.

Solution to Problem

An aspect of the present invention relates to a production method of anapped artificial leather, including the steps of: providing a fibersheet including a non-woven fabric of ultrafine fibers with a finenessof 1 dtex or less that has been impregnated with a first elasticpolymer; napping one or both surfaces of the fiber sheet to form anapped surface thereon; applying, to the napped surface, a resinsolution containing a second elastic polymer having solubility in apredetermined solvent; and applying the predetermined solvent to thesurface to which the resin solution is applied.

Another aspect of the present invention relates to a napped artificialleather including a fiber sheet obtained by impregnating a first elasticpolymer into a non-woven fabric that is an entangled body of ultrafinefibers with a fineness of 1 dtex or less, wherein the fiber sheetincludes, on one or both surfaces thereof, a napped surface obtained bythe ultrafine fibers, and further includes a second elastic polymer thatis fixed to basal portions of the napped ultrafine fibers and isunevenly distributed on a surface layer of the fiber sheet. Such anapped artificial leather has excellent pilling resistance.

Advantageous Effects of Invention

According to the present invention, it is possible to obtain a nappedartificial leather having high pilling resistance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view, in the thickness direction,of a napped artificial leather according to an embodiment of the presentinvention.

FIG. 2 is an SEM image showing a cross section, in the thicknessdirection, of a napped artificial leather obtained in Example 1, showingthe vicinity of a surface layer.

DESCRIPTION OF EMBODIMENT

First, a napped artificial leather according to an embodiment of thepresent invention will be described with reference to the drawings. FIG.1 is a schematic diagram of a cross section, in the thickness direction,of a napped artificial leather 10 according to the present embodiment.

As shown in the schematic cross-sectional view in FIG. 1, the nappedartificial leather 10 includes a non-woven fabric 1 that is an entangledbody of ultrafine fibers 1 a with a fineness of 1 dtex or less. Thenon-woven fabric 1 is formed as a fiber bundle, for example. A firstelastic polymer 2 is provided in the internal voids of an inner layer ofthe non-woven fabric 1. The first elastic polymer 2 imparts fullness tothe non-woven fabric 1. The outer side of the non-woven fabric 1 has anapped surface S on which napped ultrafine fibers 1 a are present. Also,a second elastic polymer 3 is fixed to the basal portions of the nappedultrafine fibers.

The napped artificial leather according to the present embodiment willnow be described in detail, in conjunction with an exemplary productionmethod thereof.

The napped artificial leather of the present embodiment can be obtainedby a production method including the steps of: providing a fiber sheetincluding a non-woven fabric of ultrafine fibers with a fineness of 1dtex or less that has been impregnated with a first elastic polymer;napping one or both surfaces of the fiber sheet to form a napped surfacethereon; applying, to the napped surface, a resin solution containing asecond elastic polymer having solubility in a predetermined solvent; andapplying the predetermined solvent to the surface to which the resinsolution is applied.

In the production method of a napped artificial leather according to thepresent embodiment, first, a fiber sheet is produced by impregnating afirst elastic polymer into a non-woven fabric that is an entangled bodyof ultrafine fibers with a fineness of 1 dtex or less.

In the production of the non-woven fabric, first, a fiber web ofultrafine fiber-generating fibers is produced. Examples of theproduction method of the fiber web include a method involvingmelt-spinning ultrafine fiber-generating fibers and directly collectingthe resultant fibers as filaments (continuous fibers) withoutintentionally cutting them, and a method involving cutting the resultantfibers into staples and subjecting them to a known entangling treatment.Here, “filaments” are fibers that have not been subjected to cutting.From the viewpoint of sufficiently increasing the fiber density, thelength of the filaments is preferably 100 mm or more, more preferably200 mm or more. The upper limit for the length of the filaments is notparticularly limited, and may be several meters, several hundred meters,several kilometers, or longer, and continuously spun. Among these, it isparticularly preferable to produce a filament web of ultrafinefiber-generating fibers from the viewpoint of obtaining a nappedartificial leather that is less likely to cause falling out of fibersand has excellent pilling resistance. In the present embodiment, theproduction of a filament web of ultrafine fiber-generating fibers willbe described in detail as a representative example.

Here, “ultrafine fiber-generating fiber” refers to a fiber that forms anultrafine fiber with a small fineness as a result of being subjected toa chemical or physical post-treatment after being spun. Specificexamples thereof include an island-in-the-sea composite fiber in whichan island component polymer serving as a domain different from a seacomponent polymer serving as the matrix is dispersed in the seacomponent polymer on the fiber cross section, and the sea component islater removed to form a fiber bundle-like ultrafine fiber composedmainly of the island component polymer; and a strip/division-typecomposite fiber in which a plurality of different resin components arealternately disposed around the periphery of a fiber to form a petalineshape or a superposed shape, and the fiber is divided as a result of theresin components being stripped from the fiber by a physical treatment,thereby forming a bundle-like ultrafine fiber. The use of theisland-in-the-sea composite fiber can prevent damage to the fibers suchas cracking, bending, and breaking during an entangling treatment, whichwill be described below. In the present embodiment, the formation ofultrafine fibers by using the island-in-the-sea composite fiber will bedescribed in detail as a representative example.

The island-in-the-sea composite fiber is a multicomponent compositefiber composed of at least two polymers, and has a cross section onwhich an island component polymer is dispersed in a matrix composed of asea component polymer. A filament web of the island-in-the-sea compositefiber is formed by melt-spinning the island-in-the-sea composite fiberand directly collecting the resultant fiber as a filament on a netwithout cutting it.

The island component polymer is not particularly limited so long as itis a polymer capable of forming an ultrafine fiber. Specific examplesthereof include polyester resins such as polyethylene terephthalate(PET), polytrimethylene terephthalate (PTT), polybutylene terephthalateand an elastic polymer or modified products thereof with isophthalicacid or the like; polyamide resins such as polyamide 6, polyamide 66,polyamide 610, polyamide 12, an aromatic polyamide, a semi-aromaticpolyamide, an elastic polymer or modified products thereof; polyolefinresins such as polypropylene; and polyurethane resins such as apolyester polyurethane. Among these, polyester resins such as PET, PTT,PBT and modified polyesters thereof are preferable in that they areeasily shrinkable by a heat treatment and thus can provide a nappedartificial leather having fullness. Also, polyamide resins such aspolyamide 6 and polyamide 66 are preferable in that they can provide anultrafine filament having hygroscopicity and pliability as compared withthose obtained by polyester resins, and thus can provide a nappedartificial leather having fluffiness and a soft texture.

As the sea component polymer, a polymer having higher solubility in asolvent or higher decomposability by a decomposition agent than those ofthe island component polymer is selected. Also, a polymer having lowaffinity for the island component polymer and a smaller melt viscosityand/or surface tension than the island component polymer under thespinning condition is preferable in terms of the excellent stability inspinning of the island-in-the-sea composite fiber. Specific examples ofthe sea component polymer satisfying such conditions include awater-soluble polyvinyl alcohol resin (water-soluble PVA), polyethylene,polypropylene, polystyrene, an ethylene-propylene copolymer, anethylene-vinyl acetate copolymer, a styrene-ethylene copolymer, and astyrene-acrylic copolymer. Among these, the water-soluble PVA ispreferable in that it can be removed by dissolution by using an aqueousmedium without using an organic solvent and thus has a low environmentalload.

The island-in-the-sea composite fiber can be produced by melt spinningin which the sea component polymer and the island component polymer aremelt-extruded from a multicomponent fiber spinning spinneret. Thetemperature of the multicomponent fiber spinning spinneret is notparticularly limited so long as it is a temperature at which meltspinning can be performed and is higher than both the melting points ofthe sea component polymer and the island component polymer, but isusually selected from the range of 180 to 350° C.

The fineness of the island-in-the-sea composite fiber is notparticularly limited, but is preferably 0.5 to 10 dtex, more preferably0.7 to 5 dtex. An average area ratio between the sea component polymerand the island component polymer on the cross section of theisland-in-the-sea composite fiber is preferably 5/95 to 70/30, morepreferably 10/90 to 50/50. The number of domains of the island componenton the cross section of the island-in-the-sea composite fiber is notparticularly limited, but is preferably about 5 to 1000, more preferablyabout 10 to 300, from the viewpoint of the industrial productivity.

The molten island-in-the-sea composite fiber discharged from thespinneret is cooled by a cooling apparatus, and is further drawn out andattenuated with a high-velocity air stream at a velocity correspondingto a take-up speed of 1000 to 6000 m/min by a suction apparatus such asan air jet nozzle so as to have a desired fineness. Then, the drawn andattenuated filaments are piled on a collection surface of a movable netor the like, thereby obtaining a filament web. Note that, in order tostabilize the shape, a part of the filament web may be furtherpressure-bonded by pressing the filament web if necessary. The weightper area of the filament web thus obtained is not particularly limited,but is preferably in the range of 10 to 1000 g/m², for example.

Then, the obtained filament web is subjected to an entangling treatment,thereby producing an entangled web.

Specific examples of the entangling treatment for the filament webinclude a treatment in which a plurality of layers of filament webs aresuperposed in the thickness direction by using a cross lapper or thelike, and subsequently needle-punched simultaneously or alternately fromboth sides such that at least one barb penetrates the web.

In addition, an oil solution, an antistatic agent, or the like may beadded to the filament web in any stage from the spinning step to theentangling treatment of the island-in-the-sea composite fiber.Furthermore, if necessary, the entangled state of the filament web maybe densified in advance by performing a shrinking treatment in which thefilament web is immersed in warm water at about 70 to 150° C. The fiberdensity may be increased by performing hot pressing after needlepunching so as to provide shape stability. The weight per area of theentangled web thus obtained is preferably in the range of about 100 to2000 g/m².

If necessary, the entangled web may be subjected to a treatment forincreasing the fiber density and the degree of entanglement by heatshrinking the entangled web. Specific examples of the heat shrinkingtreatment include a method involving bringing the entangled web intocontact with water vapor, and a method involving applying water to theentangled web, and subsequently heating the water applied to theentangled web by using hot air or electromagnetic waves such as infraredrays. If necessary, hot pressing may be performed. By performing hotpressing, it is possible to further densify the entangled web that hasbeen densified by the heat-shrinking treatment, fix the shape of theentangled web, and smooth the surface thereof.

The change in the weight per area of the entangled web during theheat-shrinking treatment step is preferably 1.1 times (mass ratio) ormore, more preferably 1.3 times or more and 2 times or less, furtherpreferably 1.6 times or less, as compared with the weight per areabefore the shrinking treatment.

Then, the sea component polymer is removed from the island-in-the-seacomposite fiber in the entangled web that has been densified, therebyobtaining an ultrafine filament non-woven fabric that is an entangledbody of fiber bundle-like ultrafine filaments. As the method forremoving the sea component polymer from the island-in-the-sea compositefiber, a method involving treating the entangled web with a solvent ordecomposition agent capable of selectively removing only the seacomponent polymer can be used without any particular limitation.Specifically, in the case of using the water-soluble PVA as the seacomponent polymer, for example, it is preferable to use hot water as thesolvent. In the case of using a modified polyester that is easilydecomposed by alkali as the sea component polymer, it is preferable touse an alkaline decomposition agent such as an aqueous sodium hydroxidesolution.

In the case of using the water-soluble PVA as the sea component polymer,it is preferable to remove the water-soluble PVA by extraction until theremoval rate of the water-soluble PVA becomes about 95 to 100 mass % bytreating the web in hot water at 85 to 100° C. for 100 to 600 seconds.Note that the water-soluble PVA can be efficiently removed by extractionby repeating a dip-nipping treatment. The use of the water-soluble PVAis preferable in terms of a low environmental load and reducedgeneration of VOCs since the sea component polymer can be selectivelyremoved without using an organic solvent.

The fineness of the ultrafine fiber formed in this manner is preferably1 dtex or less, more preferably 0.001 to 1 dtex, further preferably0.002 to 0.2 dtex.

The weight per area of the ultrafine filament non-woven fabric thusobtained is preferably 140 to 3000 g/m², more preferably 200 to 2000g/m². The apparent density of the ultrafine filament non-woven fabric ispreferably 0.45 g/cm³ or more, more preferably 0.55 g/cm³ or more inthat a dense non-woven fabric can be formed, thus obtaining a non-wovenfabric with fullness. Although the upper limit is not particularlylimited, the apparent density is preferably 0.70 g/cm³ or less in that apliable texture can be obtained and excellent productivity can also beachieved.

In the production of a napped artificial leather according to thepresent embodiment, a first elastic polymer is impregnated into theinternal voids of the ultrafine filament non-woven fabric before orafter generating an ultrafine fiber from an ultrafine fiber-generatingfiber such as an island-in-the-sea composite fiber. The first elasticpolymer imparts shape stability and fullness to the non-woven fabric.

Specific examples of the first elastic polymer include polyurethane, anacrylic resin elastic polymer, an acrylonitrile resin elastic polymer,an olefin resin elastic polymer, and a polyester resin elastic polymer.As the first elastic polymer, it is preferable to use an elastic polymerhaving low solubility in a solvent for dissolving a second elasticpolymer, which will be described below, and it is more preferable to usean elastic polymer having low solubility in the solvent as a result offorming a cross-linked structure after being solidified. As such anelastic polymer having low solubility in the aforementioned solvent, itis preferable to use an aqueous polyurethane that forms a cross-linkedstructure after being solidified.

An aqueous polyurethane refers to a polyurethane emulsion, or apolyurethane that is solidified from a polyurethane dispersion dispersedin an aqueous solvent. The aqueous polyurethane usually has insolubilityor low solubility in an organic solvent, and forms a cross-linkedstructure after being solidified. When the emulsion has thermal gelationproperties, the emulsion particles are thermally gelled withoutmigration, thus making it possible to evenly apply the first elasticpolymer to the fiber-entangled body.

Examples of the method for impregnating the first elastic polymer intothe non-woven fabric include a dry method in which an emulsion,dispersion or solution containing the first elastic polymer isimpregnated into an entangled web before generating an ultrafine fiberor a non-woven fabric after generating an ultrafine fiber, followed bydrying and solidification, and a method in which the solidification isperformed by a wet method. Here, in the case of using an elastic polymersuch as an aqueous polyurethane that forms a cross-linked structureafter being solidified, a curing treatment in which the polymer isheat-treated after being solidified and dried may be performed in orderto promote crosslinking, if necessary.

Examples of the method for impregnating the emulsion, dispersion orsolution of the first elastic polymer include dip-nipping in which atreatment of nipping by a press roll or the like to achieve apredetermined impregnated state is performed once or a plurality oftimes, bar coating, knife coating, roll coating, comma coating, andspray coating.

Note that the first elastic polymer may further contain a colorant suchas a dye or a pigment, a coagulation regulator, an antioxidant, anultraviolet absorber, a fluorescent agent, an antifungal agent, apenetrant, an antifoaming agent, a lubricant, a water-repellent agent,an oil-repellent agent, a thickener, a filler, a curing accelerator, afoaming agent, a water-soluble polymer compound such as polyvinylalcohol or carboxymethyl cellulose, inorganic fine particles, and aconductive agent, so long as the effects of the present invention arenot impaired.

The content ratio of the first elastic polymer is preferably 0.1 to 60mass %, more preferably 0.5 to 60 mass %, particularly preferably 1 to50 mass %, relative to the mass of the ultrafine fiber, in terms of thegood balance between the fullness and the pliability or the like of theresulting napped artificial leather.

In this manner, a fiber sheet that is a non-woven fabric of ultrafinefibers with a fineness of 1 dtex or less that has been impregnated withthe first elastic polymer is obtained. The fiber sheet thus obtained issliced into a plurality of pieces or ground in a direction perpendicularto the thickness direction so as to regulate the thickness thereof ifnecessary, and is subsequently napped by being buffed on at least onesurface by using abrasive paper such as sand paper or emery paper. Thenumber of the abrasive paper is preferably about 120 to 800, morepreferably about 320 to 600. In this manner, a napped surface obtainedby napping one or both surfaces of the fiber sheet is formed.

The thickness of the napped fiber sheet is not particularly limited, butis preferably 0.2 to 4 mm, more preferably 0.5 to 2.5 mm.

Next, a resin solution containing a second elastic polymer havingsolubility in a predetermined solvent is applied to the napped surfaceof the fiber sheet thus obtained, and subsequently the second elasticpolymer is solidified.

The second elastic polymer soluble in a predetermined solvent is anelastic polymer that is dissolved in the predetermined solvent in alater step, and subsequently solidified from the dissolved state. As thesecond elastic polymer, it is possible to use any elastic polymer havingsolubility in a predetermined organic solvent without any particularlimitation.

Specific examples of the second elastic polymer include polyurethane, anacrylic resin elastic polymer, an acrylonitrile resin elastic polymer,an olefin resin elastic polymer, a polyester resin elastic polymer thathave solubility in a predetermined organic solvent. As the secondelastic polymer, it is possible to use an elastic polymer havingsolubility in a predetermined organic solvent, and also an elasticpolymer that does not form a cross-linked structure after beingsolidified and thus has solubility in the predetermined organic solvent.As such an elastic polymer having solubility in the predeterminedorganic solvent, it is preferable to use a solvent-based polyurethanethat does not form a cross-linked structure after being solidified.

The solvent-based polyurethane having solubility in an organic solventrefers to a polyurethane obtained by reacting, at a predetermined molarratio, at least one polymer diol selected from polyester diol, polyetherdiol, polycarbonate diol and the like having an average molecular weightof, for example, 500 to 3000, at least one diisocyanate selected fromaromatic, cycloaliphatic, and aliphatic diisocyanates such as4,4′-diphenyl methane diisocyanate, isophorone diisocyanate andhexamethylene diisocyanate, and at least one low-molecular weightcompound having two or more active hydrogen atoms. If necessary, thepolyurethane may be used as a polymer composition to which a polymersuch as a synthetic rubber or a polyester elastomer is added. Thesolvent-based polyurethane can easily form a high elongation film ascompared with the aqueous polyurethane that forms a cross-linkedstructure.

The solubility in a predetermined solvent corresponds to a rate ofdissolution of preferably 70% or more, more preferably 90% or more, therate of dissolution being obtained by immersing an elastic polymer sheethaving a thickness of, for example, 100 μm in a predetermined solvent atroom temperature for 24 hours, subsequently filtrating the solvent,drying the resulting residue, measuring the mass, and using thefollowing expression: Rate of dissolution (%)=(1−Weight ofresidue/Weight of sheet before immersion in solvent)×100. Meanwhile, theinsolubility in a predetermined solvent corresponds to a rate ofdissolution of preferably 30% or less, more preferably 10% or less.

The method for applying a resin solution containing the second elasticpolymer to the napped surface of the fiber sheet include gravurecoating, bar coating, knife coating, roll coating, comma coating, andspray coating.

The second elastic polymer is applied to the napped surface of the fibersheet by applying a resin solution containing the second elastic polymerto the napped surface of the fiber sheet, and, if necessary, drying andsolidifying the resin solution.

The second elastic polymer may also further contain a colorant such as adye or a pigment, a coagulation regulator, an antioxidant, anultraviolet absorber, a fluorescent agent, an antifungal agent, apenetrant, an antifoaming agent, a lubricant, a water-repellent agent,an oil-repellent agent, a thickener, a filler, a curing accelerator, afoaming agent, a water-soluble polymer compound such as polyvinylalcohol or carboxymethyl cellulose, inorganic fine particles, aconductive agent and the like, so long as the effects of the presentinvention are not impaired.

The content ratio of the second elastic polymer relative to the mass ofthe fiber sheet is preferably 0.00001 to 0.01 mass %, more preferably0.0001 to 0.001 mass %, from the viewpoint of achieving a good balancebetween the fullness and pliability or the like of the resulting nappedartificial leather and appropriately constraining the napped fibers. Anexcessively high content ratio of the second elastic polymer tends togive rise to a hard surface and generation of fine creases.

Note that the weight per area of the second elastic polymer ispreferably 0.0001 to 0.1 times, more preferably 0.001 to 0.05 times theweight per area of the above-described first elastic polymer from theviewpoint of achieving a good balance between the fullness andpliability or the like of the artificial leather and appropriatelyconstraining the napped fibers.

Next, a solvent for dissolving the second elastic polymer is applied tothe surface to which the second elastic polymer has been applied. Bythis step, at least a part of the second elastic polymer that has beenapplied to the napped surface of the fiber sheet is dissolved and sunkin the direction of the inner layer, and dried and solidified. Then, thesecond elastic polymer is fixed to the basal portions of the nappedultrafine fibers present on the napped surface. In particular, it ispreferable that the second elastic polymer is fixed to the basalportions of the napped ultrafine fibers and is present in the form of athin film or layer on the surface layer of the napped surface of thefiber sheet. Then, as a result of the basal portions of the ultrafinefibers present on the napped surface being constrained by the secondelastic polymer, the ultrafine fibers become less likely to fall off andless likely to stick out from the inside to the outside even when thenapped surface is rubbed. As a result, it is possible to suppress theoccurrence of pilling in which the detached fibers and the sticking-outfibers form fuzz balls due to the rubbing of the surface.

Examples of the method for applying the solvent for dissolving thesecond elastic polymer to the surface to which the second elasticpolymer has been applied include, but are not particularly limited to,gravure coating, bar coating, knife coating, roll coating, commacoating, and spray coating.

As the solvent for dissolving the second elastic polymer, any solventhaving solubility to dissolve the second elastic polymer simply by beingapplied can be used without any particular limitation. Such a solventmay be selected as appropriate according to the type of the secondelastic polymer. Specific examples thereof include ketones such ascyclohexanone and methyl ethyl ketone (MEK), N,N-dimethylformamide(DMF), dimethyl acetamide (DMA), N-methyl pyrrolidone, dimethylsulfonamide (DMSO), in the case of dissolving a solvent-basedpolyurethane, for example. A solvent mixture obtained by mixing theabove-described solvents at a predetermined ratio may be used, or a poorsolvent of the first elastic polymer may be mixed.

While the amount of application of the solvent for dissolving the secondelastic polymer may be adjusted as appropriate according to the balancebetween the desired texture and properties, the thickness or the like,it is preferable that the solvent is applied in an amount of preferablyabout 1 to 50 g/m², more preferably about 5 to 30 g/m². When the amountof application of the solvent is too large, the second elastic polymertends to be excessively dissolved and excessively permeated into theinner layer. When the amount of application is too small, the secondelastic polymer will not be sufficiently dissolved, and thus, it tendsto be difficult for the basal portions of the napped ultrafine fibers tobe sufficiently fixed.

In the napped artificial leather of the present embodiment, it ispreferable that the second elastic polymer 3 has permeated into thefiber sheet and fixed to the basal portions of the napped ultrafinefibers 1 a, and is unevenly distributed in the form of a thin film orlayer on the surface layer of the napped surface 1 a of the fiber sheet,as shown in the SEM image of FIG. 2, for example. An average thicknessof the portion where the second elastic polymer is present in the formof a thin film or layer is preferably 5 to 60 μm, more preferably 10 to40 μm, from the viewpoint of obtaining a pliable napped artificialleather. When the portion where the second elastic polymer is present istoo thick, the surface layer portion tends to be hard, or fine creasestend to be formed on the surface. When the portion where the secondelastic polymer is present is too thin, the effect of the nappedultrafine fibers in fixing the second elastic polymer tends to bereduced, resulting in a reduction in the pilling suppressing effect.

In the napped artificial leather of the present embodiment, an averageratio of the thickness of the portion where the second elastic polymeris present, relative to the thickness of the fiber sheet, is preferably1 to 20%, more preferably 5 to 10%. When the ratio of the thickness ofthe portion where the second elastic polymer is present relative to thethickness of the fiber sheet is too high, the fiber sheet tends to havea hard texture.

In this manner, a napped artificial leather of the present embodiment isobtained. The length of the napped fibers of the napped artificialleather according to the present embodiment is not particularly limited,but is preferably 1 to 500 μm, more preferably 30 to 200 μm, from theviewpoint of providing a napped artificial leather having fine shortfibers resembling those of a natural nubuck leather. Note that thelength of the napped fibers can be determined, for example, by capturinga cross-sectional image with a scanning electron microscope (SEM) in astate in which the napped fibers on the surface of the napped artificialleather are manually raised, measuring the length of arbitrarilyselected 50 fibers, the length extending from the entangled surface,which is the basal portion, to the upper end thereof, and calculating anaverage value thereof.

The apparent density of the napped artificial leather according to thepresent embodiment is preferably 0.4 to 0.7 g/cm³, more preferably 0.5to 0.6 g/cm³, from the viewpoint of achieving a good balance betweenpliability and fullness. Furthermore, the weight per area of the nappedartificial leather according to the present embodiment is preferably 150to 1000 g/m², more preferably 200 to 600 g/m², from the viewpoint ofachieving a good balance between pliability and fullness.

Note that the napped artificial leather of the present embodiment isdyed as needed. A suitable dye is selected as appropriate according tothe type of the ultrafine fibers. For example, when the ultrafine fibersare formed from a polyester resin, it is preferable that the nappedartificial leather are dyed with a disperse dye. Specific examples ofthe disperse dye include benzene azo-based dyes (e.g., monoazo anddisazo), heterocyclic azo-based dyes (e.g., thiazole azo, benzothiazoleazo, quinoline azo, pyridine azo, imidazole azo, and thiophene azo),anthraquinone-based dyes, and condensate-based dyes (e.g.,quinophthalone, styryl, and coumarin). These are commercially availableas dyes with the prefix “Disperse”, for example. These may be used aloneor in a combination of two or more. As the dyeing method, it is possibleto use a high-pressure jet dyeing method, a jigger dyeing method, athermosol continuous dyeing machine method, a dyeing method using asublimation printing process, and the like without any particularlimitation.

The napped artificial leather of the present embodiment may be furthersubjected to a flexibilizing treatment by crumpling or a relaxingtreatment to adjust the texture, or a finishing treatment such as areverse seal brushing treatment, an antifouling treatment, ahydrophilization treatment, a lubricant treatment, a softener treatment,an antioxidant treatment, an ultraviolet absorber treatment, afluorescent agent treatment and a flame retardant treatment.

Since the napped fibers that have been once napped are fixed to thesurface of the fiber sheet by the second elastic polymer, the nappedfibers are less likely to be pulled out even when dyeing or a relaxingtreatment is performed.

In this manner, a napped artificial leather of the present embodimentthat has been adjusted such that the ultrafine fibers whose basalportions are constrained by the elastic polymer are present on thenapped surface is obtained. Such a napped artificial leather cansuppress the occurrence of pilling in which the detached fibers or thesticking-out fibers form fuzz balls even when the napped surface isrubbed.

EXAMPLES

Hereinafter, the present invention will be described in further detailby way of examples. It should be appreciated that the scope of thepresent invention is by no means limited by the examples.

Example 1

Ethylene-modified polyvinyl alcohol as a thermoplastic resin serving asa sea component and isophthalic acid-modified PET as a thermoplasticresin serving as an island component were molten separately. Note thatthe ethylene-modified polyvinyl alcohol had an ethylene unit content of8.5 mol %, and a degree of polymerization of 380 and a saponificationdegree of 98.7 mol %. The isophthalic acid-modified PET had anisophthalic acid unit content of 6.0 mol % and a melting point of 110°C. Then, each of the molten resins was supplied to a multicomponentfiber spinning spinneret having many nozzle holes disposed in parallelfor forming a cross section on which 25 island component portions havinguniform cross-sectional areas were distributed in the sea component. Atthis time, the molten resins were supplied by adjusting the pressuresuch that the mass ratio between the molten resin serving as a seacomponent and the molten resin serving as an island component satisfiesSea component/Island component=25/75. Then, molten resin strands havinga cross section with an island-in-the-sea structure were discharged fromthe nozzle holes set at a spinneret temperature of 260° C.

Then, the molten resin strands discharged from the nozzle holes werestretched by suction by an air jet nozzle suction apparatus with an airstream pressure regulated so as to provide an average spinning speed of3700 m/min, and thereby to spin island-in-the-sea composite filamentswith a fineness of 2.1 dtex. The spun island-in-the-sear compositefilaments were continuously piled on a movable net while being suctionedfrom the back side of the net. The piled amount was regulated byregulating the movement speed of the net. Then, in order to suppress thefuzzing on the surface, the island-in-the-sea composite filaments piledon the net were softly pressed with a metal roll at 42° C. Then, theisland-in-the-sea composite filaments were removed from the net, andallowed to pass between a grid-patterned metal roll having a surfacetemperature of 75° C. and a back roll, thereby hot pressing the fiberswith a linear load of 200 N/mm. In this manner, a filament web having aweight per area of 34 g/m² and in which the fibers on the surface weretemporarily fused in a grid pattern was obtained.

Next, an oil solution mixed with an antistatic agent was sprayed to thesurface of the obtained filament web. Then, 10 sheets of the filamentweb were stacked by using a cross lapper apparatus to form a superposedweb with a weight per area of 340 g/m², and an oil solution forpreventing the needle from breaking was further sprayed thereto. Then,the superposed filament web was needle-punched, thereby performing athree-dimensional entangling treatment. Specifically, the stacked bodywas needle-punched at a density of 3300 punch/cm² alternately from bothsides by using 6-barb needles with a distance of 3.2 mm from the needletip to the first barb at a punching depth of 8.3 mm. The area shrinkageby the needle punching was 18%, and the weight per area of the entangledweb after the needle punching was 415 g/m².

The obtained entangled web was densified by being subjected to aheat-moisture shrinking treatment. Specifically, water at 18° C. wasuniformly sprayed in an amount of 10 mass % to the entangled web, andthe entangled web was heat-treated by being stood still in an atmospherewith a temperature of 70° C. and a relative humidity of 95% for 3minutes with no tension applied, thereby heat-moist shrinking theentangled web so as to increase the fiber density. The area shrinkage bythe heat-moisture shrinking treatment was 45%, and the densifiedentangled web had a weight per area of 750 g/m² and an apparent densityof 0.52 g/cm³. Then, for further densification, the entangled web waspressed with a dry-heat roll, thereby adjusting the apparent density to0.60 g/cm³.

Next, an emulsion of the first elastic polymer with a solid contentconcentration of 30% was impregnated into the densified entangled web.Note that the first elastic polymer was an aqueous polyurethane composedmainly of a polycarbonate/ether polyurethane capable of forming across-linked structure after being solidified and having a rate ofdissolution of 5% in a solvent mixture described below. Then, theimpregnated emulsion of the first elastic polymer was dried in a dryermachine at 150° C., thereby solidifying the aqueous polyurethane in thedensified entangled web.

Next, the entangled web to which the aqueous polyurethane had beenapplied was immersed in hot water at 95° C. for 20 minutes, therebyremoving the sea component contained in the island-in-the-sea compositefilaments by extraction. Then, the entangled web was dried in a dryermachine at 120° C., thereby obtaining a fiber sheet that included anon-woven fabric of ultrafine filaments with a fineness of 0.08 dtex andto which the aqueous polyurethane had been applied. The mass ratio ofthe non-woven fabric to the aqueous polyurethane in the fiber sheet was87/13. Then, the fiber sheet was sliced into halves in the thicknessdirection, and the surface thereof was napped by being buffed with sandpaper with a number of 600.

Next, as a solution containing the second elastic polymer, a solution ofa solvent-based polyurethane substantially completely soluble in asolvent mixture of 5% DMF and 95% cyclohexanone was prepared as follows.

260 parts by mass of polyester diol with a number-average molecularweight of 2000, 620 parts by mass of polyhexylene carbonate with anumber-average molecular weight of 2000, 580 parts by mass ofpolybutylene adipate with a number-average molecular weight of 2000, 540parts by mass of polytetramethylene glycol with a number-averagemolecular weight of 2000, 217 parts by mass of ethylene glycol, 1149parts by mass of diphenyl methane-4,4′-diisocyanate, and 10100 parts bymass of DMF were charged into a reactor, and allowed to react under astream of nitrogen, to produce a polyurethane solution with aweight-average molecular weight of 360000. Note that the polyester diolwith a number-average molecular weight of 2000 contained an equimolarmixture of N-methyldiethanolamine and 3-methyl-1,5-pentane diol as thediol component and sebacic acid as the dicarboxylic acid component.

Then, cyclohexanone was added to the polyurethane solution to adjust thesolid content to 5%. Then, the polyurethane solution with a solidcontent of 5% was applied in an amount of 11 g/m² to the outer side ofthe napped surface of the fiber sheet by using a 200-mesh gravurecoater, and subsequently dried. At this time, the weight per area ratioof the solvent-based polyurethane to the aqueous polyurethane providedearlier (solvent-based polyurethane/aqueous polyurethane) was 0.012times.

Then, the solvent mixture of 5% DMF and 95% cyclohexanone for dissolvingthe solvent-based polyurethane was applied in an amount of 10 g/m² tothe outer side of the napped surface of the non-woven fabric by using a200-mesh gravure coater, and subsequently dried.

Then, the napped artificial leather was scalded in hot water at 80° C.for 20 minutes to relax the leather with the hot water, and subsequentlydyed into black by using a high-pressure jet dyeing machine (circulardyeing machine from HISAKA WORKS, LTD.).

In this manner, a dyed napped artificial leather that included anon-woven fabric of ultrafine filaments with a fineness of 0.08 dtex andhad a napped surface on one surface was obtained. FIG. 2 shows an SEMimage showing a cross section, in the thickness direction, of the nappedartificial leather obtained in Example 1. The obtained napped artificialleather had a thickness of 0.6 mm, a weight per area of 350 g/m², and anapparent density of 0.58 g/cm³. The length of the napped fibers wasabout 80 μm. The second elastic polymer was permeated into the fibersheet, was fixed to the basal portions of the napped ultrafine fibers,and was unevenly distributed in the forms of a layer on the surfacelayer of the fiber sheet. The average thickness of that layer was 25 μm.

Then, the obtained napped artificial leather was evaluated for thepilling resistance, the surface appearance, and the texture in thefollowing manner. The results are summarized in Table 1.

[Pilling Resistance]

Testing was performed by using a Martindale abrasion tester inaccordance with ISO 12945-2, and evaluation was made according to thefollowing grading criteria.

5: No change was observed.

4: Slight surface fuzzing and/or fuzz balls formed in some portions ofthe surface were observed.

3: Medium level of surface fuzzing and/or medium level of pilling, andfuzz balls with various sizes and densities appearing in some portionsof the test strip surface were observed.

2: Clear surface fuzzing and/or clear pilling, and fuzz balls withvarious sizes and densities were observed in most portions of the teststrip surface.

1: Dense surface fuzzing and/or significant pilling, and fuzz balls withvarious sizes and densities covering the entire surface of the teststrip were observed.

[Surface Appearance]

The appearance of the obtained napped artificial leather was observedvisually, and evaluated according to the following criteria.

3: Nubuck-like, fine short fibers were observed.

2: Suede-like, somewhat coarse napped fibers were observed, or somecreases were observed on the surface.

1: The nap length was clearly uneven, or creases were prominentlyobserved.

[Texture]

The obtained napped artificial leather was bent, and the differences inelasticity and flexibility compared with a napped natural leather wereevaluated according to the following criteria.

3: A texture with a good balance between fullness and flexibility, closeto the texture of the napped natural leather, was observed.

2: A texture harder than that of the napped natural leather wasobserved.

1: A texture with poorer fullness than that of the napped naturalleather was observed.

TABLE 1 Weight per area ratio between Evaluation results polymer SolventFiber Nap Pilling Surface Example First elastic Second elastic elasticbodies application length length resistance appearance Texture No.polymer polymer (Second/First) step mm μm (5 to 1) (3 to 1) (3 to 1) 1Aqueous Solvent-based 0.012 Performed filament 80 5 3 3 polyurethanepolyurethane 2 Aqueous Solvent-based 0.012 Performed 51 80 5 3 3polyurethane polyurethane 3 Solvent-based Solvent-based 0.012 Performedfilament 60 5 2 3 polyurethane polyurethane 4 Aqueous Solvent-based0.025 Performed filament 40 5 2 3 polyurethane polyurethane 5 AqueousSolvent-based 0.004 Performed filament 180 4 3 3 polyurethanepolyurethane 6 Aqueous Solvent-based 0.0012 Performed filament 300 4 2 3polyurethane polyurethane 7 Aqueous Solvent-based 0.05 Performedfilament 20 5 2 3 polyurethane polyurethane Com. Aqueous Solvent-based0.012 Not filament 20 3 2 3 Ex. 1 polyurethane polyurethane performedCom. Aqueous Aqueous 0.012 Performed filament 300 4 2 3 Ex. 2polyurethane polyurethane Com. Aqueous — — Performed filament 400 3 2 3Ex. 3 polyurethane

Example 2

Using ethylene-modified polyvinyl alcohol as a thermoplastic resinserving as a sea component and isophthalic acid-modified PET as athermoplastic resin serving as an island component, an island-in-the-seacomposite fiber was melt-spun such that the mass ratio between the seacomponent and the island component satisfied Sea component/Islandcomponent=25/75, then stretched, crimped and cut, thereby obtainingshort fibers (staples) of island-in-the-sea composite fibers with afineness of 2.1 dtex and an average fiber length of 51 mm.

Then, the obtained short fibers were formed into a cross-lapped web byusing a webber, and needle-punched at a density of 700 punch/cm² byusing a needle punching machine, to obtain an entangled web with aweight per area of 407 g/m².

Then, a napped artificial leather including a non-woven fabric having anapped surface on one surface was obtained in the same manner as inExample 1 except that the entangled web with a weight per area of 407g/m² obtained as above was used in place of the entangled web with aweight per area of 415 g/m² used in Example 1. The obtained nappedartificial leather had a thickness of 0.6 mm, a weight per area of 340g/m², and an apparent density of 0.57 g/cm³. The length of the nappedfibers was about 80 μm. The second elastic polymer was permeated in thefiber sheet, was fixed to the basal portions of the napped ultrafinefibers, and was unevenly distributed in the form of a layer on thesurface layer of the fiber sheet. The average thickness of that layerwas 25 μm.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Example 3

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that the solvent-based polyurethane used as the second elasticpolymer in Example 1 was impregnated as the first elastic polymer intothe densified entangled web such that the mass ratio of the modified PETto the solvent-based polyurethane was 87/13 instead of impregnating theemulsion of the aqueous polyurethane as the first elastic polymer inExample 1. The obtained napped artificial leather had a thickness of 0.6mm, a weight per area of 350 g/m², and an apparent density of 0.58g/cm³. The length of the napped fibers was about 60 μm. The secondelastic polymer was permeated into the fiber sheet, was fixed to thebasal portions of the napped ultrafine fibers, and was unevenlydistributed in the form of a layer on the surface layer of the fibersheet. The average thickness of that layer was 22 μm.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Example 4

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that the weight per area ratio of the solvent-based polyurethaneto the aqueous polyurethane (solvent-based polyurethane/aqueouspolyurethane) was changed from 0.012 times used in Example 1 to 0.025times. The obtained napped artificial leather had a thickness of 0.6 mm,a weight per area of 350 g/m², and an apparent density of 0.58 g/cm³.The length of the napped fibers was about 40 μm. The second elasticpolymer was permeated into the fiber sheet, was fixed to the basalportions of the napped ultrafine fibers, and was unevenly distributed inthe form of a layer on the surface layer of the fiber sheet. The averagethickness of that layer was 35 μm.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Example 5

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that the weight per area ratio of the solvent-based polyurethaneto the aqueous polyurethane (solvent-based polyurethane/aqueouspolyurethane) was changed from 0.012 times used in Example 1 to 0.004times. The obtained napped artificial leather had a thickness of 0.6 mm,a weight per area of 350/m², and an apparent density of 0.58 g/cm³. Thelength of the napped fibers was about 180 μm. The second elastic polymerwas permeated into the fiber sheet, was fixed to the basal portions ofthe napped ultrafine fibers, and was unevenly distributed in the form ofa layer on the surface layer of the fiber sheet. The average thicknessof that layer was 15 μm.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Example 6

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that the weight per area ratio of the solvent-based polyurethaneto the aqueous polyurethane (solvent-based polyurethane/aqueouspolyurethane) was changed from 0.012 times used in Example 1 to 0.0012times. The obtained napped artificial leather had a thickness of 0.6 mm,a weight per area of 350 g/m², and an apparent density of 0.58 g/cm³.The length of the napped fibers was about 300 μm. The second elasticpolymer was permeated into the fiber sheet, was fixed to the basalportions of the napped ultrafine fibers, and was unevenly distributed inthe form of a layer on the surface layer of the fiber sheet. The averagethickness of that layer was 10 μm.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Example 7

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that the weight per area ratio of the solvent-based polyurethaneto the aqueous polyurethane (solvent-based polyurethane/aqueouspolyurethane) was changed from 0.012 times used in Example 1 to 0.05times. The obtained napped artificial leather had a thickness of 0.6 mm,a weight per area of 355 g/m², and an apparent density of 0.59 g/cm³.The length of the napped fibers was about 20 μm. The second elasticpolymer was permeated into the fiber sheet, was fixed to the basalportions of the napped ultrafine fibers, and was unevenly distributed inthe form of a layer on the surface layer of the fiber sheet. The averagethickness of that layer was 45 μm.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Comparative Example 1

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that the step of applying the solvent mixture performed inExample 1 was omitted. The obtained napped artificial leather had athickness of 0.6 mm, a weight per area of 350 g/m², and an apparentdensity of 0.58 g/cm³. The length of the napped fibers was about 20 μm,but exhibited uneven nap and had prominent small creases on the surface.Although the second elastic polymer was fixed to the upper portions andthe basal portions of the napped ultrafine fibers and unevenlydistributed in the form of a layer on the surface layer of the fibersheet, the permeation of the second elastic polymer in the thicknessdirection of the fiber sheet was not observed.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Comparative Example 2

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that an emulsion of an aqueous polyurethane that was the same asthe one used as the first elastic polymer in Example 1 was appliedinstead of applying the solvent-based polyurethane as the second elasticpolymer in Example 1. The obtained napped artificial leather had athickness of 0.6 mm and a weight per area of 350 g/m². The length of thenapped fibers was about 300 μm. The second elastic polymer wasdiscontinuously fixed to the upper portions of the napped ultrafinefibers, and the permeation of the second elastic polymer in thethickness direction of the fiber sheet was not observed. Also, a partialdetachment was observed during dyeing.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

Comparative Example 3

A napped artificial leather including a non-woven fabric having a nappedsurface on one surface was obtained in the same manner as in Example 1except that a solvent mixture that was the same as the one used inExample 1 was applied, without applying the second elastic polymer. Theobtained napped artificial leather had a thickness of 0.6 mm and aweight per area of 350 g/m². The length of the napped fibers was about400 μm.

Then, the obtained napped artificial leather was evaluated in the samemanner as in Example 1. The results are shown in Table 1.

All of the napped artificial leathers obtained in Examples 1 to 7 hadgrade 4 or above according to the pilling resistance grading criteria,and had high pilling resistance. Note that since Example 3 used thesolvent-based polyurethane soluble in the solvent as the first elasticpolymer, the application of the solvent caused the first polymer to bepartially dissolved, and as a result, a somewhat hard texture with finecreases on the surface was observed. The napped artificial leatherobtained in Example 6, which had a low weight per area ratio of thesolvent-based polyurethane to the aqueous polyurethane, exhibited a weakconstraint on the napped ultrafine fibers and thus had grade 4, whichwas somewhat low, according to the pilling resistance grading criteria.The napped artificial leather obtained in Example 7, which had a highweight per area ratio of the solvent-based polyurethane to the aqueouspolyurethane, had a somewhat hard surface, and as a result, fine creaseswere observed on the surface.

On the other hand, the napped artificial leather of Comparative Example1, in which the step of applying the solvent mixture for dissolving thesolvent-based polyurethane to the outer side of the napped surface wasomitted, had grade 3 according to the pilling resistance gradingcriteria. The napped artificial leather of Comparative Example 2, inwhich the aqueous polyurethane insoluble in the solvent was applied tothe outer side of the napped surface instead of applying thesolvent-based polyurethane, had grade 2 according to the surfaceappearance grading criteria. From the results of Example 1 andComparative Examples 1 and 2, it can be seen that, in order to improvethe pilling resistance and obtain fine nubuck, the elastic polymer needsto be dissolved in the solvent and be permeated in the direction of theinner layer so as to be solidified at the basal portions of theultrafine fibers. The napped artificial leather obtained in ComparativeExample 3, in which the application of the elastic polymer was omittedand only the solvent was applied, had a long nap length and exhibited anuneven nap.

The production method of a napped artificial leather described in detailthus far includes the steps of: providing a fiber sheet including anon-woven fabric of ultrafine fibers with a fineness of 1 dtex or lessthat has been impregnated with a first elastic polymer; napping one orboth surfaces of the fiber sheet to form a napped surface thereon;applying, to the napped surface, a resin solution containing a secondelastic polymer having solubility in a predetermined solvent; andapplying the solvent to the surface to which the resin solution isapplied. With this production method of a napped artificial leather, thesecond elastic polymer provided in the surface layer of the nappedsurface is dissolved and permeated in the direction of inner layer byapplication of the solvent, and subsequently solidified by evaporationof the solvent, and thereby fixed to the vicinity of the basal portionsof the napped ultrafine fibers. Then, the napped ultrafine fibers areconstrained by the second elastic polymer, and thus become less likelyto be detached or to stick out to the outside even when the nappedsurface is rubbed. As a result, it is possible to suppress theoccurrence of so-called pilling in which ultrafine fibers are detachedor stick out by the surface being rubbed, and the ultrafine fibers areentangled to form masses.

Preferably, the first elastic polymer that is pre-impregnated into thefiber sheet is an elastic polymer having insolubility in the solvent.When the first elastic polymer is soluble in the solvent, the firstelastic polymer is also dissolved, together with the second elasticpolymer, by the application of the solvent. Accordingly, the texturebecomes hard, for example, and it tends be difficult to control theproduct quality control.

It is preferable that the first elastic polymer is an elastic polymerthat forms a cross-linked structure, and the second elastic polymer isan elastic polymer that does not form a cross-linked structure, sincethe first elastic polymer is less likely to be dissolved in theabove-described solvent and the second elastic polymer is likely to bedissolved in the solvent.

The first elastic polymer is preferably, for example, an aqueouspolyurethane, and the second elastic polymer is preferably asolvent-based polyurethane, since the resulting napped artificialleather has well-balanced properties, and an aqueous polyurethane, ingeneral, forms a cross-linked structure and thus has low solubility,whereas a solvent-based polyurethane does not form a cross-linkedstructure and thus has high solubility.

It is preferable that the ultrafine fibers are filaments in that theultrafine fibers tend not to fall off.

It is preferable that the second elastic polymer has a weight per areathat is 0.0001 to 0.05 times a weight per area of the first elasticpolymer, from the viewpoint of improving the pilling resistance whilepreventing the texture from becoming too hard.

A napped artificial leather includes a fiber sheet obtained byimpregnating a first elastic polymer into a non-woven fabric that is anentangled body of ultrafine fibers with a fineness of 1 dtex or less,wherein the fiber sheet includes, on one or both surfaces thereof, anapped surface formed by the napped ultrafine fibers, and furtherincludes a second elastic polymer that is fixed to basal portions of thenapped ultrafine fibers and is unevenly distributed on a surface layerof the fiber sheet. Such a napped artificial leather has excellentpilling resistance.

It is preferable that the napped ultrafine fibers have a nap length of30 to 200 μm since a napped artificial leather have fine short fibersresembling those of a natural nubuck leather can be obtained.

INDUSTRIAL APPLICABILITY

A napped artificial leather obtained by the present invention can bepreferably used as a skin material for clothing, shoes, articles offurniture, car sheets, general merchandise, and the like.

REFERENCE SIGNS LIST

-   1 a . . . Ultrafine fibers-   1 . . . . Non-woven fabric-   2 . . . . First elastic polymer-   3 . . . . Second elastic polymer-   10 . . . Napped artificial leather-   s . . . Napped surface

1. A production method of a napped artificial leather, comprising thesteps of: providing a fiber sheet including a non-woven fabric ofultrafine fibers with a fineness of 1 dtex or less that has beenimpregnated with a first elastic polymer; napping one or both surfacesof the fiber sheet to form a napped surface thereon; applying, to thenapped surface, a resin solution containing a second elastic polymerhaving solubility in a predetermined solvent; and applying the solventto the surface to which the resin solution is applied.
 2. The productionmethod of a napped artificial leather in accordance with claim 1,wherein the first elastic polymer is an elastic polymer havinginsolubility in the solvent.
 3. The production method of a nappedartificial leather in accordance with claim 2, wherein the solubilitycorresponds to a rate of dissolution in the solvent of 90% or more, andthe insolubility corresponds to a rate of dissolution in the solvent of10% or less.
 4. The production method of a napped artificial leather inaccordance with claim 2, wherein the first elastic polymer is an elasticpolymer that forms a cross-linked structure, and the second elasticpolymer is an elastic polymer that does not form a cross-linkedstructure.
 5. The production method of a napped artificial leather inaccordance with claim 1, wherein the first elastic polymer is an aqueouspolyurethane, and the second elastic polymer is a solvent-basedpolyurethane.
 6. The production method of a napped artificial leather inaccordance with claim 1, wherein the ultrafine fibers are filaments. 7.The production method of a napped artificial leather in accordance withclaim 1, wherein the second elastic polymer has a weight per area thatis 0.001 to 0.05 times a weight per area of the first elastic polymer.8. A napped artificial leather produced by the production method ofclaim 1, comprising a fiber sheet obtained by impregnating a firstelastic polymer into a non-woven fabric that is an entangled body ofultrafine fibers with a fineness of 1 dtex or less, wherein the fibersheet includes, on one or both surfaces thereof, a napped surface formedby the napped ultrafine fibers, and further includes a second elasticpolymer that is fixed to basal portions of the napped ultrafine fibersand is unevenly distributed on a surface layer of the fiber sheet. 9.The napped artificial leather in accordance with claim 8, wherein thefirst elastic polymer has insolubility in a predetermined solvent, andthe second elastic polymer has solubility in the solvent.
 10. The nappedartificial leather in accordance with claim 9, wherein the solubilitycorresponds to a rate of dissolution in the solvent of 90% or more, andthe insolubility corresponds to a rate of dissolution in the solvent of10% or less.
 11. The napped artificial leather in accordance with claim8, wherein the first elastic polymer is an aqueous polyurethane, and thesecond elastic polymer is a solvent-based polyurethane.
 12. The nappedartificial leather in accordance with claim 11, wherein the aqueouspolyurethane has a cross-linked structure, and the solvent-basedpolyurethane does not have a cross-linked structure.
 13. The nappedartificial leather in accordance with claim 8, wherein the secondelastic polymer is permeated into and unevenly distributed on thesurface layer of the fiber sheet in a form of a layer or film, and aregion where the second elastic polymer is permeated into and unevenlydistributed has an average thickness of 5 to 60 μm.
 14. The nappedartificial leather in accordance with claim 8, wherein the ultrafinefibers are filaments.
 15. The napped artificial leather in accordancewith claim 8, wherein the second elastic polymer has a weight per areathat is 0.001 to 0.05 times a weight per area of the first elasticpolymer.
 16. The napped artificial leather in accordance with claim 8,wherein the napped ultrafine fibers have a nap length of 30 to 200 μm.